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trouble with flow simulation

Question asked by Dan Hofstetter on Jan 30, 2015
Latest reply on Feb 3, 2015 by Jared Conway

I have been having some trouble with a flow simulation where I am getting a very high velocity near an outlet volume flow boundary condition.  I have tried many things to eliminate this:  using overlapping lids at a flow opening and defining outlet volume flow, velocity, and mass flow rates, as well as leaving a solid boundary and defining a split line to use as the outlet.  I also noticed when inspecting average face velocities at the outlet that the Area (Fluid) matches the geometry correctly, i.e. an 8" diameter circle is shown as 0.349 sq.ft., but the surface area shown next to the velocity is always lower (0.346 sq.ft.).  To work around this, I added a local initial mesh to the outlet face and set the All Cells refinement level to 4 or 5.  This helps to capture the surface area, but I'm still getting some weird numbers.

 

For instance, with a 14.5" diameter flow outlet at 1,302 cfm, the velocity should equal 18.9 ft/s, but I'm seeing min = 18.97, max = 87.4, average = 27.2 ft/s.  I think that one high velocity is throwing it all off, but I can't seem to get rid of it.  When I look at the velocity cut plot and show the min/max locations, I can see that this velocity occurs in one cell that is near the edge of the outlet.  Have any of you seen this problem, and can you recommend a fix?  I've attached my 2015 version flow model in case anyone wants to take a look.

 

Thanks,

 

Dan

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